A Mobile Station (MS) usually operates according to a method shown in FIG. 1 to access a network. Herein, the access to the network may include reentry to the network.
FIG. 1 is a diagram illustrating an operation between an MS and a Base Station (BS) in order for the MS to access the network in a conventional mobile communication system.
Referring to FIG. 1, in step 101, the MS performs downlink synchronization. In step 102, the MS obtains system information from the BS. The system information generally includes access codes and access opportunity information.
In step 103, the MS accesses the network after performing backoff processing.
In step 104, the MS sends an Initial Reference Code (IRC) to a Base Station (BS) included in a ranging opportunity. In this step, when the MS has no available ranging opportunity, e.g., when the access operation has expired or the number of access operations exceeds a threshold, step 104 is continued or the access operation is terminated, the factors of which may be determined according to practical applications.
In step 105, the MS receives a Ranging-Acknowledgement (RNG-ACK) message or an Advanced Air Interface_Ranging-Acknowledgement (AAI_RNG-ACK) message from the BS, where the RNG-ACK message includes a response of the BS to the detected IRC.
In step 106, the BS sends a Code Division Multiple Access (CDMA) Allocation A-MAP Information Element (IE) message to the MS to allocate Ranging-Request (RNG-REQ) resources to the MS.
In step 107, the MS sends a RNG-REQ message to the BS after receiving the CDMA Allocation A-MAP IE message to inform the BS of information containing an Identifier (ID) of the MS, and then continues accessing the network.
In step 108, the BS sends a Ranging-Response (RNG-RSP) message to the MS and allocates a temporary Station Identifier (STID) to the MS.
In step 109, after the MS receives the RNG-RSP message, the BS and the MS perform capability negotiation, the MS sends a Registration-Request (REG-REQ) message to the BS, and then the BS sends a Registration-Response (REG-RSP) message that includes the STID to the MS.
Thus, through steps 101 through 109, the operation in which the MS accesses the network is completed.
Further, the MS may operate in the following order to access the network.
First, the MS obtains system information. Second, the MS sends an IRC to the BS in a ranging opportunity.
Again, the MS listens to and receives a RNG-ACK message or a CDMA Allocation A-MAP IE message from the BS, where the RNG-ACK message or the CDMA Allocation A-MAP IE message includes a response of the BS to the detected IRC. In this step, according to receiving instances, the MS may obtain the system information or terminate the access operation because of various factors, which may be determined according to practical applications. For example, the access operation may be terminated when the MS does not receive the response to the IRC sent by the MS and does not have an available ranging opportunity, e.g., when the access operation has expired, the number of access operations exceeds a threshold or, when the response received by the MS indicates “abort”. According to receiving instances, the MS may send the IRC to the BS, for example, when the MS does not receive the response to the IRC sent by the MS and has an available ranging opportunity, or when the response received by the MS indicates “continue”. When the response indicates “abort”, the BS may configure a timer for the MS, and when the timer has timed out, the MS may access the network again.
When sending the IRC to the BS, the MS randomly selects the ranging opportunity and the IRC according to a backoff window.
Finally, the MS continues accessing the network after the MS receives the RNG-ACK message indicating “success” and/or the CDMA Allocation A-MAP IE message, and sends a RNG-REQ message to the BS to inform the BS of information containing an ID of the MS.
As can be seen from the above description, the conventional procedure that the MS accesses the network may be applicable to a single MS. In addition, the conventional MS obtains the IRC first when accessing the network, the IRC is selected randomly when the MS accesses the network, and the number of available IRCs is finite. Therefore, the conventional network access method for the MS may result in a conflict, such as when two or more MSs inadvertently select the same IRC, the MSs sending the same IRC may not all access the network successfully or all the MSs sending the same IRC may not access the network successfully. Especially, with the development of Machine to Machine (M2M) technology, more MSs may access the network at the same time, which increases the possibility of conflict, and thus result in that some MSs cannot access the network successfully.